Conventionally, microelectromechanical systems (MEMS) microphones can comprise a MEMS chip attached to a substrate. These MEMS chips are generally enclosed by a cover or lid forming a single acoustic back cavity. An acoustic input can be provided from an opening on a top surface of the microphone such as on the cover or lid or from an opening on the substrate. Typically, in conventional applications where the acoustic input is from the top, an acoustic back cavity is formed mainly by a volume under the MEMS chip and the substrate. By contrast, in conventional applications where the acoustic input is from the bottom, an acoustic back cavity is typically formed by the volume enclosed by the substrate and the cover or lid.
However, acoustic characteristics such as sensitivity, frequency response, etc. of such conventional MEMS microphones are limited by the MEMS microphones' device characteristics and the physical constraints imposed on the geometry of the package by the end user application, and as such, conventional MEMS microphones are typically limited in their capability for tuning the acoustic characteristics. In addition, such configurations of conventional MEMS microphones typically lack robustness in terms of absorbing acoustic shock. For example, conventional MEMS microphones can have difficulty withstanding an extreme acoustic shock that they can be subjected to in a guided drop test that is proposed to become an industry standard.
It is thus desired to provide MEMS microphones that improve upon these and other deficiencies. The above-described deficiencies of MEMS microphones are merely intended to provide an overview of some of the problems of conventional implementations, and are not intended to be exhaustive. Other problems with conventional implementations and techniques and corresponding benefits of the various aspects described herein may become further apparent upon review of the following description.